I would describe all motor as being naturally aspirated (meaning no Turbos, Superchargers or Nitrous). Power adders are all thing that give more HP and Torque (cams, exhaust, headers, engine electronics ect...)
Techtonics Tuning is the US had a rabbit GTI run LOW 12's consistently in the early-mid 80's. No forced induction, No nitrous. They even used the stock CIS injection system. It was powered by a 1.8 8V bored out to 2 litres(i think) along with many other mods.